Power supply circuit with LM723 - Power Circuit - Circuit Diagram

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LM723 application circuit - LM723 regulated power supply circuit, its reference voltage is small external interference, and its short-circuit protection, its output voltage is 0. The LM723 output voltage ranges from 2 to 37 V. If the LM723 output voltage is greater than 2 V, the V- pin can be directly grounded, but in order to achieve an output voltage of 0 V, the V- pin should be connected to a negative voltage of at least -0.4 V. There are several ways to To achieve this requirement, one uses an inverter to convert the positive voltage to a negative voltage, but this introduces noise interference. The LM273's technical manual and its internal structure show that the LM237's reference voltage and V-pin voltage are directly Relatedly, the voltage of this pin must be stable and there must be no interference, so another method is used here to get the proper voltage, as shown in Figure 2, in the circuit, VREF=1.28 V is U2A, R19 R5 and R6 are obtained from the reference voltage of LM723, which is inverted by amplifier U2B, R1, R2, at node VM256=-2.56 V, which is to complete a negative feedback to VREF, partially compensated for the temperature The influence of the voltage makes the reference voltage stable. Here, R19 is an adjustable resistor that can control the voltage of VM256 point to a suitable value, so that the reference voltage of the output of LM723 can be fine-tuned.

The TC1321DAC is connected to the IN pin of the LM732 to set the output voltage. The TCl321 has a 10-bit resolution, 2.7-5.5 V output voltage, integral differential linearity and an output voltage offset of less than 8 mV. The DAC is controlled by the internal CPU of Butterfly via the I2C bus. Its reference voltage VREF=1.28 V. The output voltage of the DAC is passed through a simple low-pass filter (consisting of R7 and Cs) to smooth out the output voltage and remove glitches.